Brain and Behavior Psych exam 1

what is neuroscience

not a single field, but studied by scientists from many backgrounds (biology, psychology, medicine, chemistry, etc)

behavioral neuroscience

the field that studies the relationship between behavior and the body, especially the brain

behavior includes both…. (example?)

the body and the brain

for example, holding a warm beverage can make you feel emotionally ‘warm’ toward someone (physical sensations in the body can influence emotions and thoughts, not just brain activity)

overt behaviors vs internal events

behavior can be both:

overt behaviors- observable actions (walking, speaking, eating)

internal events- mental processes like learning, thinking, emotions

controllable vs uncontrollable behaviors

controllable- deciding to study, choosing to speak

uncontrollable- hunger and thirst

what is the mind-brain problem

the question of what the mind is and how it relates to the brain

asks how mental experiences relate to the brain

what does the mind refer to

mind refers to experience, both conscious and unconscious

includes thoughts, feelings, perceptions, and memories

two main viewpoints relating to the mind-brain problem

monism and dualism

monism

belief that the mind and body are. made of the same substance

everything that exists is physical; mind = brain activity

focuses on things that can be observed and measured

dualism

belief that mind and body are separate

mind is non-physical; body/brain is physical

what is a model

a proposed mechanism explaining how something works

what do models emerge from?

rationalism (knowledge through reasoning alone) and empiricism (knowledge through observation and experimentation)

what did early scientists help move psychology toward?

physical explanations for brain and behaviors

Descartes

believed in dualism; thought the mind and brain were separate, but connected

from this, he proposed a model of behavior: behavior controlled by “animal spirits” flowing through nerves

believed the pineal gland housed the soul; chose this because it’s one of the only brain structures not strongly divided into left and right halves

what idea did Descartes help push?

that behavior has physical mechanisms; this is important historically

Galvani (1700s)

electrically stimulated frog nerves

observed muscle contraction in frog legs

concluded that electricity plays a role in nerve signaling

Gustav Fritsch and Eduard Hitzig (1870)

showed electrical stimulation of the brain caused movement

supported the idea that the brain uses electrical signals

what problem was discovered with the electrical brain?

electricity travels at the speed of light, but the brain and body react much slower

Hermann con Helmholtz

measured nerve conduction speed, and found it was only ~25-40 meters per second, much slower than light

Helmholtz’s conclusion

nerves don’t work like simple electrical wires

neural signaling involves more than just electricity (chemistry is involved too)

localization

the idea that specific brain areas carry out specific functions (ex- occipital lobe = vision)

equipotentiality

idea that the brain functions as an undifferentiated whole (no spcific areas with specialized roles)

phrenology

localization taken too far:

claimed personality traits (like criminality) were located in specific brain areas

judged by bumps on the skull

not scientific, but historically important because it shows the danger of overinterpreting localization

evidence for localization

broca: studied patients with speech problems, and found damage to the front portion of the brain (later called Broca’s area)

these patients could understand language, but could not produce speech (speech is slow, effortful, and grammatically incorrect; comprehension, however, is intact)

provided real scientific evidence that certain brain regions are responsible for specific functions

modern neuroscience view

modern monism

lateralization

for most people, language is lateralized to the left hemisphere (especially common in right handed males)

this, however is not universal, showing that localization is not identical for everyone (reveals equipotentiality, since functions aren’t perfectly fixed in every individual)

who is phineas gage / what implications did he have

Gage, in the 1800s, had an iron rod pass through his skull. he survived and physically recovered

after the injury, he had major personality changes: increased anger, poor impulse control, alcohol abuse

this matters because he damaged his frontal lobe, which involves decision making, reasoning, personality, and emotional regulation

**injury caused widespread damage, so its not perfect localization evidence, but still informative

functional brain map

cases like Broca and Gage helped develop a functional brain map, which reveals which regions are responsible for what activities

major cortical areas of the brain

motor cortex (controls voluntary movement)

somatosensory cortex (processes: touch, pressure, pain, temp, vibration)

occipital lobe (vision)

temporal lobe (auditory processing - hearing)

** mappings come from patterns across many patients, not one single case

language comprehension

Wernicke’s Area - involved in language comprehension

Wernicke’s Aphasia has fluent and grammatically correct speech, but content makes little or no sense and patient doesn’t understand language

Broca’s vs Wernicke’s aphasia

broca: trouble producing speech, speech is slow and effortful, and comprehension is intact

weknicke’s: trouble understanding speech, speech sounds normal, comprehension is impraired

nature vs nuture

debate over genetic inheritance (nature) and environmental influence (nurture)

modern view: psychologists agree most behaviors are influenced by both, except certain physical traits, like eye color

**so, genetics matter, but aren’t ‘destiny’

foundations of the genetic code

DNA, genes, alleles

DNA (deoxyribonucleic)

double stranded double helix

chemical instructions for building and maintaining cells

gene

a unit of DNA: directs cellular processes, transmits inherited traits

alleles

different versions of the same gene

create genetic diversity

dominant allele

expressed if at least one copy is present

recessive allele

expressed only if two copies are present

heterozygous

two different alleles

homozygous

two identical alleles

recessive traits require which genotype?

homozygous

blood type with dominant vs recessive alleles

A and B → dominant

O → recessive

AB → both dominant alleles expressed

genotype vs phenotype

genotype: your genetic makeup, combination of alleles

phenotype: observable traits, what is actually expressed

environment can affect phenotype even with the same genotype: genotype is like the instructions, and phenotype is how those instructions actually show up; the environment can change how strongly, when, or even if certain genes are expressed

• two people can have the same genes, but look, behave, or function differently since they grew up in diff environments (like nutrition, stress, illness)

X linked traits

genes located on the X chromosome

males are effected more since they only have one X chromosome, while females have 2, so one can compensate

**reason for colorblindness being more common in males

polygenic traits

determined by multiple genes (height, intelligence, and psychological traits)

autoimmune diseases

often polygenic, and require environmental triggers (nature and nurture working together)

heredity

the transmission of genetic traits from parents to offspring. (explains why individuals differ within a population)

genes provide predispositions, not guarantees

natural selection

traits that increase survival and reproduction become more common (operates at a population level, not individual like heredity)

environment-specific

only matters up until reproductive age (only ‘cares’ about traits that affect survival to reproductive age, and ability to reproduce)

example- sickle cell trait provides malaria resistance in certain environments

heritability

percentage of variation in a trait within a population due to genetics; doesn’t mean that trait is fixed or inevitable

vulnerability

genes increase the risk for disorders; environment determines whether they develop

what is a theory

A framework that integrates and explains many observations about a phenomenon.

• well supported explanation, not guesses

• example- gravity is still considered a theory because the particle it relies on hasn’t been directly observed, yet its effects are consistently demonstrated

inductive reasoning process

process of building theories: observation → pattern/generalization → theory

example: darwin:

• observed birds on different islands had different beaks → inferred different functions → developed the theory of natural selection

why must theories be thorough and constantly tested?

because one counterexample can challenge a theory

deductive reasoning

testing theories: process- theory → predictions → experiments

if a theory is true, then a specific outcome should occur

• ex- if gravity exists, objects thrown into the air should fall back down

tentative nature of science

science doesn’t prove ideas, it attempts to disprove them; similar to stats- we reject or fail to reject hypothesis

scientists use tentative language (no absolute certainty, only increasing confidence over time)

why is scientific knowledge always subject to change?

• studies may be flawed

• new data can change interpretation

• results may occur due to chance (laws of probability)

observation in science

broadly defined and may include:

• watching behavior

• neurological measurements

• surveys and self reports

naturalistic observation

observing behavior in real world settings

high realism, low control

case studies

in depth examination of one individual

useful for understanding unique or rare cases (like phineas gage), but limited generalizability

surveys

collect self reported data

example- cortisol linked to stress through self reports

limitation- variables may be related to multiple factors

experimental studies

researcher manipulates the independent variable to observe changes in the dependent variable

goal is to ensure the independent variable is the only possible cause of changes in the dependent variable

random assignment in experimental studies

helps to eliminate confounding variables

trade off in experimental studies

high control, but lower realism

correlational studies

measures two or more variables to see if they are relates; useful for studying real-world phenomena, but can’t establish cause and effect relationships since it’s vulnerable to confounding variables

often misrepresented in scientific journalism

staining and imaging neurons

neurons are highly interconnected, making them difficult to image → staining helps visualize structure and activity

golgi stain

randomly stains about 5% of neurons

useful because it reveals individual neurons clearly and can show developmental changes (fewer cell bodies over time, much greater interconnectedness — newborn to 1 month to 6 months to 2 years)

helps identify neuron structure and composition

myelin sheath

binds to fatty myelin around axon

highlight areas with many information sending neurons

most concentrated in subcortical structures

nissl stain

labels neuron cell bodies

cell bodies are concentrated in cortical structures

autoradiology

identifies which neurons are active by staining them

immunocytochemistry

uses antibodies tagged with dye to label specific cell components

light microscopy

magnification up to 1,500x

limited for viewing fine cellular detail

electron microscopy

magnification up to 250,000x (and higher)

transmission electron microscope (TEM)

electron beam passes through thin tissue slices

can magnify up to 50 millionX

electroencephalography (EEG)

measures electrical activity across the scalp

amplifiers detect summed activity of many neurons between electrodes

temporal resolution of EEG

extremely high (as precise as 1 millisecond)

captures moment to moment elctrical activity on the brain’s surface

spatial resolution of EEG

poor unless electrodes are placed directly on the brain

event related potentials (ERP)

EEG activity time locked to specific events or stimuli

derived from EEG recordings

provide excellent temporal resolution (within milliseconds) → can provide detect timing close to when individual neurons fire

strength/limitation of ERP

strength- tells us when something happens in the brain

limitation- poor spatial resolution → not good for identifying where in the brain activity occurs

stereotaxic instrument

device that allows positioning of probes within the brain

uses a 3D coordinate system based on anatomical landmarks

essential for targeting very specific brain regions

• Probes typically fine-wire electrodes

• Microelectrodes can monitor and stimulate a single neuron

• Can treat patients with Alzheimer's and Parkinson’s

natural experiments

historically, brain damaged patients were crucial to neuroscience research (Phineas Gage)

limitations- damage often overlaps multiple functional areas

• may not destroy an entire functional region

• makes cause and effect conclusions difficult

ablation

surgical removal of brain tissue

researches remove progressively smaller areas to isolate function

typically used for large, accessible brain regions

limitation- difficult to remove small or deep structures without damaging surrounding tissue

lesioning

surgical damage to neural tissue (not necessarily removal)

more precise than ablation

can be temporary or reversible

allows stronger causal claims than natural experiments

Transcranial Magnetic Stimulation (TMS)

noninvasive technique that uses a magnetic coil to induce electrical activity in the brain → coil is held over the scalp and pulsed at different rates

can temporarily disrupt or enhance neural activity; used in research and therapy (for depression)

no known long term effects

historical context of brain imaging techniques

before modern imaging, brain studies relied on post mortem observations

Computed Tomography (CT)

uses a series of X-rays to create a 3D image

images show differing densities of blood vessels in the brain (increased blood vessel levels = increased brain activity, or can imply tumors/cancer, can also pick up aneurysms → thinning of the lining of blood vessels)

doesn’t pick up on any brain activities (just infers about more blood vessels being more active)

positron emission tomography (PET) scan

observation of brain regions through a radioactive substance injected into the blood stream

scanner picks up emitted positrons to form a color coded image

indicates relative activity of brain regions

benefits/limitations of PET scan

negative- exposes to radiation, can’t detect changes less than 30 sec in duration, doesn’t provide detailed brain structure

positive- good for looking at more wide scale brain area, indicates relative brain regions

Magnetic Resonance Imaging (MRI)

measures radio-frequency waves emitted by hydrogen atoms exposed to magnetic field

• most hydrogen atoms are within water molecules in the brain

• provides detailed structural images

Diffusion Tensor Imaging (DTI)

MRI variant that measures movement of water molecules

used to visualize white matter tracts and neural connections

functional MRI (fMRI)

detects changes in blood flow and oxygen use

indicates brain activity indirectly

strengths/limitations of fMRI

strengths- good spatial resolution, can detect changes within 1 second, suitable for repeated measurements, no radiation so safer than PET

limitation- very expensive

compare/contrast ERP, CT, PET, MRI, and fMRI

ERP- best timing, poor location

CT- structure only

PET- large scale activity, poor timing, radioactive

MRI- structure, high detail

fMRI- activity + location, expensive